Background:HMA are standard of care in pts with high-risk MDS and commonly used in pts with lower risk. Pts with high-risk disease post HMA failure have a poor prognosis with a median survival of 4-6 months. The prognosis of pts with low and intermediate-1 risk MDS by the International Prognostic Scoring System (IPSS) after HMA failure is not known.

Results: Median age was 69 years. 294 (69%) pts had a diploid cytogenetic analysis. 63 (15%) pts had therapy-related MDS. 282 (67%) pts received azacitidine, 87 (21%) decitabine, and 54 (12%) both. Median number of cycles of HMA administered was 6 (range, 1-64) for a median duration of therapy of 7 months (range, 1- 74). Best response to HMA was complete response (CR) in 39 (9%) pts, partial response (PR) in 13 (3%), a bone marrow CR in 6 (1%), and hematologic improvement (HI) in 90 (21%) pts. Pts had discontinued HMA because of primary resistance in 198 (47%) pts, loss of response in 141 pts (33%), intolerance in 13 pts (3%) and other reasons in 71 pts (17%). At the time of HMA failure, 81 (19%) pts transformed into acute myeloid leukemia (AML). Of the 302 remaining pts evaluable by IPSS, 67 (22%) pts were of low-risk, 158 (53%) of intermediate-1 risk, 48 (16%) of intermediate-2 risk, and 29 (9%) of high-risk disease. By the revised IPSS (R-IPSS), the percentage of pts with low, very low, intermediate, high, and very high risk disease were 11%, 29%, 30%, 20%, and 10%, respectively. By the MDACC global prognostic scoring system (MDGPSS) 18%, 35%, 29%, and 18%, of the pts were of low-risk, intermediate-1, intermediate-2, and high-risk disease, respectively. After a median follow-up of 16 months from HMA failure, 117 (28%) pts remained alive. The median overall survival (OS) was 15 months (95% CI: 12-18) with estimated 1- and 3-year OS rates of 55% and 27%, respectively. Both, the R-IPSS and the MDGPSS were predictive of survival post HMA failure (Table 1).

Conclusion:In the largest cohort of lower risk MDS pts treated with HMA, the outcome after HMA failure is poor. Treatment of those patients remains an unmet medical need. OS is a reasonable primary endpoint for clinical studies targeting this population.